This invention relates to the art of catheter sheath introducers and, more particularly, to improvements permitting rotational and angular movement of a cannula relative to the distal end of the housing of such an introducer.
Catheter sheath introducers are known in the art and examples are described in the patents to L. A. Weinstein U.S. Pat. No. 4,626,245 and R. C. Stevens U.S. Pat. No. 4,000,739. These catheter sheath introducers typically take the form of a molded plastic tubular housing having a distal end and a proximal end and having a passageway extending through the proximal and distal ends and the housing for slideably receiving an elongated catheter tube. The catheter tube may slide through the housing from the proximal end to the distal end before being introduced into a body vessel. A tubular cannula extends from the distal end of the housing and is adapted to be inserted into a body vessel and be in communication with the passageway through the housing. The cannula serves to guide a catheter passing through the housing and thence through the cannula and into the body vessel. Typically, the catheter sheath introducer is secured to the exterior of a body, such as on an arm, with the cannula in place within a body vessel, such as an artery. The catheter may then be slid through the introducer and be guided by the cannula into the body vessel. As is typically accomplished during angiographic procedures, the catheter serves to insert x-ray contrast fluid into a body vessel, such as an artery.
The cannula is a plastic tube which fits within the housing as by a press fit or the like, and extends therefrom so as to be inserted into the body vessel. The physician will insert the cannula tube sufficiently far into a body vessel that the distal end of the housing bears up against a patient's body, the arm, for example. The introducer is then held in place by taping it to the patient's arm. One problem that has been encountered with this procedure is that there is a tendency for the cannula to be angularly displaced relative to the distal end of the housing, causing the cannula to take on a bend or become kinked. This kinking takes place at the junction of the cannula and the distal end of the housing and causes a reduction in the inner diameter at the junction. This provides an obstruction as the physician is trying to slide a catheter through the introducer and into the cannula. Because of the small diameters employed with catheters in this procedure, any reduction in the inner diameter of the cannula tube presents difficulties for the physician in attempting to insert catheter through the introducer and thence through the cannula into a patient's body vessel.